Adam Clarke on Job 31:1

I made a covenant with mine eyes - ברית כרתי לעיני berith carati leeynai: "I have cut" or divided "the covenant sacrifice with my eyes." My conscience and my eyes are the contracting parties; God is the Judge; and I am therefore bound not to look upon any thing with a delighted or covetous eye, by which my conscience may be defiled, or my God dishonored.

Why then should I think upon a maid? - ומה אתבונן על בתולה umah ethbonen al bethulah. And why should I set myself to contemplate, or think upon, Bethulah? That Bethulah may here signify an idol, is very likely. Sanchoniatho observes, that Ouranos first introduced Baithulia when he erected animated stones, or rather, as Bochart observes, Anointed stones, which became representatives of some deity. I suppose that Job purges himself here from this species of idolatry. Probably the Baithulia were at first emblems only of the tabernacle; בית אלוה beith Eloah, "the house of God;" or of that pillar set up by Jacob, Gen 28:18, which he called בית אלהים beith Elohim, or Bethalim; for idolatry always supposes a pure and holy worship, of which it is the counterfeit. For more on the subject of the Baithulia, see the notes on Gen 28:19.